Motor rheostat for acceleration



Oct. 18, 1932. D. SANTINI MOTOR RHEOSTAT FOR ACCELERATION Filed July 24,1929 INVENTOR '/a Semi/0i Slop ' srarr- Disfiaqce ATTORNEY Patentfi i iUNITE STATES azess rarsrrr- OFFICE HOUSE ELECTRIC & EANUFACTUIBINGVAN-[A GOIIAIY, A CORPORATION OF PENNSYL- HOTOB RHEOBTA'I. FOBACCELERATION Application filed July 84,

My invention relates to control systems and has particular relation tosystems of control for elevator hoists and similar machinl in object ofmy invention is toprovide 'a control system for motors in which theacceleration and deceleration of the motor may be controlledautomatically.

Another object of my invention is to provide. a control system formotors wherein the rate of acceleration and deceleration is independentof the load upon the motor.

Another object of my invention is to provide a control system for motorshaving voltage-modifying devices for determining the speed of the motor,which devices will be automatically connected, in, and disconnectedfrom, the circuit at ratesdetermined by the load on the motor. I

My invention will be described with reference to the acco ipanyingdrawing, wherein,

Figure 1 is a diagrammatic view of an elevator-control system wherein myinvention is applied to control the acceleration and deccleration of thedriving motor; and

' F i g. 2 is a diagram embodying acceleration and deceleration curvesto illustrate the eifect of the application of my invention to thecontrol system.

I have illustrated an elevator car C suspended upon a cable Co whichpasses over a hoisting drum D to a suitable counterweight C10. Thedriving device for the hoisting drum D is of the variable-voltage typeand comprises an elevator motor EM having its armature EM directlycoupled to the hoisting drum D and having its field winding EMFconnected to a source of power indicated by the reference characters L1and L2. T he armature EM is conncctedin loop circuit with the armatureG" of a. generator G illustrated as being of the compound-wound typehaving; a separately excited field winding GF and a serics'ficld winding13?. A means for driving the generator G is illustrated as a motor hi,preferably of the shuntwound type. having its armature M directlycoupled to the armature G of the generator G and having its shunt fieldwinding HF con- 1229. Serial :0. amass.

nected in parallel relation to the arms.- ture M.

The direction and speed of operation of the hoisting motor EM isillustrated as controlled through the actuation of a car switch Cswhich, in turn, controls an up-dircction switch 1, a down-directionswitch 2 and an acceleratin switching device 9.

Ihe acce erating switching device 9 comprim a switch arm 10 pivotallymounted, as at 11, upon a suitable base (not shown) and operated in aclockwise direction by means of a. motor 12, coupled to the switch arm10, by means of a suitable reduction gearing 13.

As will be hereinafter described,it is desirable that the speedofmovcment of the switch arm 10 should be controlled in accordance withthe load upon the motor and, for this purpose, I have illustrated aneddycurrent isc 14 connected for rotary movement under the influence ofthe motor 12 b means of suitable reduction gearin 15. retarding magnet16, similar to that used to damp orretard the movement of electricmeterelements, is arranged with its pole pieces 17 and 17' on opposite sidesof the eddy-current disc 14. The magnet 16 comprises a core 18,preferably of soft iron, having thereon a voltage coil 19 and acalibrating coil 20. These coils are wound in opposition to each otherand the coils are so selected that the etiect of the voltage coil willbe in excess of that of the calibrating coil for any value of currentwhich ma be passed through the calibrating coil, un er the conditionshereinafter described.

Since it is desirable that the elevator should be arranged to be drivenat a plurality of different speeds, I have provided means for driving itat a slow landing speed, an intermediate speed and a higher speed. Whenthe elevator is being driven at the slow speed, the switch arm 10 willbe in the position shown in Fig. 1, and will be restrained in thatposition by means of the spring 21. When the car is being driven at thehigher speed. the switch arm will be in its extreme right hand position,or thereabouts, depending upon the load upon the elevator car C, andwill be restrained in that position by means of the motor 12, in amanner to be hereinafter described. When movement of switch -arm 10 willbe limited by the latching member 112.-

The latching member 23 normally extends into the path of travel of thelug 22, under the influence of the spring 29. Its extended end is soconstructed that, when the switch arm 10 is moving in a clockwisedirection, its motion is limited by the position of hitching member 23but, when the switch arm 10 is moving in a counter-clockwise direction,

I position,

latching member 23 presents a surface to the lug 22 at such an anglethat the force exerted on switch. arm 10 by the spring 21 is sufiicientto depress the latching member'23 and allow switch arm 10 to pass.Latching member 23 is retractable from its normal position by means of asuitable electromagnetic releasing coil 23',.conne'ctible forene'rgization by operation of the car switch Cs. latching member 24 issimilar to latching member 23 but is disposed in .the' reverse positionand arranged to be normally retracted, under the influence of a tensionsprin 30. It will be noted, therefore, that when atching member 24 is inthe extended it will limit the motion of switch arm 10 but will permitit to pass when moving in the clockwise direction. 1

The latching member 112 also normall extends into the path of the lug 22on switc arm 10, under the influence of its spring 115. Latehing member112 is wound with two coils 112 and 112", the former of which isconnected in series relation with the armature of the generator G andthe latter of which is connected across the terminals of the enerat'orG. These coils are so arranged on the armature of latching member112that, under conditions of positive load, their magnetomotive forceswill be additive and, under conditions of negative load, will besubtractive. They are so designed that their combined influence issuiiicient to actuate latching member 112 to retract it from itsnormally extended position. When they are opposing, the member 112 willof course not be actuated. In a manner tobo hereinafter described,latching member 112 acts to keep the motor speed constant underconditions of 7 positive and negative load.

It is apparent that the lZONEIB developed by the motor 12 should alwayse in the same The in the counter-clockwise direction direction,independent of whether the car is moving upwardly er the e 'evator motoris driving the load or being driven by the load to return power totheline. vided a reverse-power relay 5 and two auxiliary directionswitches-3 and 4.

The reverse-power relay 5 is provided with two coils 27 and 28, theformer of which is connected in series relationwith the armatures 'ofthe generator and motor and the latter of which is connected across theterminals of the generator G.

The coils 27 and 28 are so disposed upon the core of reverse-power relay5 that, when the elevator load is positive in either the up or the downdirect-ion,-1. e. when theclevator To accomplish this, I have proordownwardly, or wheththe magnetomotive forces of the two coils aresubtractive and the relay assumes its normal position.

'The response to power reversal when the car is moving in a givendirection, determined, by the character of the load, as positive ornegative, provided for by reversepower relay 5, is transmitted to thearmature of motor 12 through the auxiliary direction switches 3 and 4,the coils of which are connected to the source of power through thenormally open .contactmembers, respective ly, of reverse-power relay 5,as will be hereinafter described. The reversal of current flow,dependent upon the direction of travel of the car C, is transmitted tothe armature of the motor 12 by meansof contact members on the reversingdirection switches 1 and-2, so that the current supplied to the armature12 will always be in a direction to-cause the motor to exert torque inthe same direction independent ofthe character of the load.

It is, of course, necessarythat the motor 12 shall exert torque onlyduring acceleration of the car. To this end, I have provided that itsarmature circuit may be controlled through either of two relays 6 and 7,which relays are suitably controlled by the car switch Ca, in a mannerhereinafter described. It will be noted that relay 7 is suitablyinterlocked with relay 6 through a pair of normally closed con tactmembers I) on the latter relay. Relay 7 is further mechanicallyinterlocked by means of the latch member 32 of latch magnet extendibleinto the path of the hook 31 formed at the end of the armature of'relay7 by means of the coil 7 a wound on' magnet 70 and suitably controllcdby the car switch Cs.

My system will best be understood with reference to an assumedoperation. Assuming that it is desired to move the car upwardly, the carswitch Cs may be moved in,a counterclockwise direction to complete acircuit for energizing relay 7, which circuit extends from lineconductor L1, through conductor 33, contact members 34, 35 and 36 of carswitch Cs, conductors 37 and 38, normally closed contact members 6 ofrelay 6, conductor 39, the coil of switch 7 and conductor 40, to lineconductor L2. The operation of relay 7 prepares 'a circuit for thearmature of motor 12, which circuit is not completed until the operationof one of the direction switches 1 and 2 and one of the auxiliarydirection switches 3 and 4. i

If the car switch C3 is moved further in a counter-clockwise direction,a circuit is completed for energizing the.coil 7a of latch magnet 7a,which circuit extends from line conductor L1, through conductor 33,contact members 34, 35 and 41 of car switch Cs, conductors 42 and 43,the coil 7 a of latch magnet 7a, and conductors 44 and 40, to lineconductor L2. Now actuated, the latch member 32 moves to a position inthe path of movement of the member 31 on the armature of relay 7. Sincerelay 7 is already energized the actuation of latch magnet 70; iswithout efiect. However, it will be noted that if relay 7 is deenergizedwhile latch magnet 7a is energized, it will be impossible to actuaterelay 7 to again close its contacts until latch magnet 7a isdeenergized. As illlustrated, the extended end of the latch member 32 isso formed as to permit passage of the member 31 in one direction but torestrain it from movement in the opposite direction.

If the car switch C8 is now moved further in a counter-clockwisedirection, a circuit is completed for energizing the rip-directionswitch 1 and relay 8, which circuit'extends from line conductor L1,through conductor 33, contact members 34, 35 and 45 of the car switchCs, conductor 46, the'coil of up-direc tion switch 1, conductors 47 and48, the coil of relay 8, and conductor 49, to line conductor L2.

Up-direction switch 1, when actuated, completes a circuit for supplyingvoltage to the separately excited field winding GF for the generator G,which circuit extends from line, conductor L1, through conductors 50, 51and 52, contact members a on rip-direction switch 1, conductors 53 and54, separately excited field winding GF, conductors 55 and 56, contactmembers 5 on up-direction switch 1, conductor 57, resistor 58, contactmember 59 on switching device 9, contact brush 60 on switch arm 10,switch arm 10 and conductors 61 and 62, to line conductor L2. It will beobserved that resistor 58 is divided into a plurality of sections eachof which is connected in consecutive order to contact members onswitching device 9, similar to contact member 59, and arranged to beengaged by contact brush 60 carried by switch arm 10.

The separately excited field winding GF will now be supplied withcurrent corresponding to the value of resistance in the circuit, asdetermined by the size of resistor ductors 64 and 65, contact members ofrelay 8 (now energized) and conductor 66, to line conductor L1.Aspreviously described, voltage coil 19 is also energized by actuationof relay 8, byway of a circuit which extends from line-conductor L1,through conductor 66, contact members of relay 8, conductor 65, voltagecoil 19, "adjustable resistor 67 and conductors 68 and 69,.to lineconductor L2.

If we assume that the load upon the elev tor is such that the elevatormotor is draw: ing power from the generator, we may say, for example,that current is flowing through the loop circuit formed by theconnections between the generator and elevator motor armatures, la wayof the armature G of generator of elevator motor EM, conductor 71, coil112 of latching member 112, conductor 111, the field winding 12' oftorque motor 12, conductor 72, the coil 27 of reverse power relay 5.conductor 73, the series field winding GSF of generator G and conductor75, back to the generator again. Accordingly, current will flow throughthe coil 28 of reverse-power relay 5, by way of conductors 7 O and 76,the coil 28 and conductors 77 and 7 3, to the generator as described. Inthis case, then the fluxes of coils 27 and 28 will be additive, andreverse-power relay 5 will be actuated to close its normally opencontact members (1, thereby completing a circuit for the coil ofauxiliary direction switch 3, which circuit extends from line conductorL1, throu h conductors 50 and 78, contact members a o reverse-powerrelay 5, conductor 79, the coil of auxiliary direction switch 3,conductors 80 and 81, contact membars 6 of up-direction switch 1 (nowclosed) and conductors 82, 83 and 84, to line conductor L2.

When actuated, switch 3 closes its contact members a and b to complete acircuit to supswitch 1, conductors 86 and 87, contact mem-.-.

conductor 70, the armature EM V bers b of auxiliary direction switch 3,conductor 88, the armature of motor 12, conductors 90 and 91, thecontact members of relay 7, conductors 92, 93, and 89, contact members aof auxiliary reversing switch 3, conductor-s94 and 95, contact members 0of up-direct-ion switch 1 and conductors 96 and 84, to line conductorL2.

Since both the armature and field windings of motor 12 are nowenergized, the motor develops torque proportion to such energization andmoves switch arm 10 of the accelerating device 9 in a cloc wisedirection against the. opposing force of th spring 21, which movementcontinues until lug 22 on switch arm 10 encounters latching member 23.

As switch arm 10 moved in the clockwise direction, portions of resistor58 were successively excluded from the separately eX- cited fieldwinding GB of generator G, and the current through, and the flux set upby, which winding was therefore increased. As a result, therefore, thevoltage of generator G increased, and, accordingly, the speed of thehoisting motor EM increased proportionately.

Since a voltage is now developed across the terminals of generator G, acurrent will flow in the coil 112" of latching member 112. Further,since the condition of positive load was assumed, the effect upon thearmature of latching member, 112 of its two coils 112 and 112" will beadditive, and latching member 112 will therefore be retracted. It willbe noted that, at any time that the load is positive, the latchingmember 112 is retracted.

If it is desired to operate the car at its highest speed, the switcharm- Cs may be moved to its extreme position in the counterclockwisedirection. In so doing, the contact member 35 of the car switch Cs willengage contact member 98 to complete acircuit for energizing the coil 24of latching member 24, which circuit extends from line conductor- L1,through conductor 33, contact members 34, 35 and 98 of the car switchCs, conductors 99 and 100, the coil 24 of latching member 24 andconductors 101 and. 69, to line conductor L2. Its coil being. nowenergized, latching member 24 is moved to its extended position, againstthe force of its restraining spring 30. This action, however, producesno effect dun ing the acceleration of the car, but is effective duringdeceleration, as will be hereinafter described.

With the car switch in its extreme position,

two additional circuits are completed, one for energizing relay 6, andone for retracting latching member 23. The former circuit extends fromline conductor-L1, through conductor 33, contact members 34, 35 and 102of car switch Cs, conductors 103 and 104, the coil of relay 6 andconductors 105 and 40, to

line conductor L2. Its coil, now being energized, relay 6 closes itscontact members a,

and opens its contact members 1; thereby transferring control of thecircuit for the armature winding of the motor 12 from relay 7 torela-y'6. It will be noted that the closing of contact members a isimmediate, but that the opening of contact members I) is retarded by anysuitableretarding device. As illus- 7 trated, the retarding meanscomprise a spring 108 and a dash pot 107 adaptedto-retard the motion ofcontact members I) in the opening 6, the hook 31 formed at the end ofthe armature of switch 7 passed over, and was engaged by, the latchmember 32 of latching magnet 7a. .It is obv ous, therefore, that acircuit cannot be completed for the armature winding of the motor 12through relay 7 until after latching magnet 7a is deenergized to retractthe member 32, under the influence of its biasing spring 7 a The lattercircuit, completed by the movement of car switch C8 to its extremeposition, eiiected the energization of the coil of latch- ;ing member23, which circuit extendsfrom line conductor L1, through conductor 33,the

[contact members 34, 35 and 102 ofcar switch Cs, conductors 103 and 106,the coil of latching members 23 and conductors 107 and 69, to lineconductor L2. Being now energized, the coil of latching member 23 actsto retract latching member 23 from its extended position, therebyallowing the switch arm 10 to pass to its extreme position to therebyexclude additional portions of resistor 58 from the circuit of theseparately excited 'field windingGF of generator F. Hence, hoisting mo-.

tor EM accelerates to its high speed.-

It will be also observed that the rapidity with which the switch arm 10moves to any of its positions is determined by the effect of the magnet16 on-the eddy-current disc 14.

Since the voltage coil 19 is connected directlyto the source of power,the force exerted by "this coil will be constant through all movementsof the switch arm'10. However, the

calibrating coil 20, being connected in series relation with resistor58, the force 'excrted'by coil 20 will be dependent upon the value ofresistance retained inthe gen'erator-fieldwinding circuit. Since thecoils 19 and 20 are wound in opposition to each other, it follows that,during the initial movements of the switch arm 10, the eddy-current disc14 will exert its greatest retarding effect, which 'efi'ect I isdiminished as the arm 10 continues to rotate to assume new positions.Thatis, between the time that the arm-10 leaves the stop member 97 andthe engagement of the lower portion 22 of arm 10 with latch member 23,the movement of arm 10 will be slow, While the movement between latch 23and the extreme position, defined by stop member 97 more rapid. It isthe variable speed of movement of the arm 10 thus obtained to therebyexclude sections of resistor 58 at increasing rates as the car switchCsis moved to operate the motor EM at increasing 1o speeds, whlchproduces the most desirable acceleration curve for use withelevatoroperation.

It is well known that a limitation upon the rate of change of speed ofan elevator car 15 is imposed by the fixed rate at which the body of thepassenger may be accelerated without discomfort. On the other hand, ithas been observed that, if the acceleration can be started gradually,and increased thereafter, a much less discomforting effect is producedupon the passengers. I have illustrated, in Fig. 2, an accelerationcurve 108 which represents the most rapid rate of acceleration which maybe used without discomfort to passengers. An inspection of this curvewill illustrate the fact that, at the initial starting of the car fromthe point designated by legend Start, acceleration is at a.comparatively slow rate, which increases as the car attains speed. It isobvious, therefore, that, with my system of control, utilizing diiferentspeeds of movement of the switch arm 10, this desired acceleration ratemay be readily obtained.

Curve 109, illustrated in Fig. 2, represents a deceleration curve whichis in all respects similar to the acceleration curve 108, and it hasbeen observed that the rate of deceleration illustrated by curve 108 isthe most rapid I '49 leceler. tion permissible for comfort for thepassenger and also for accuracy in stopping the car level with a floorat which it is desired to stop.

It will be observed that, after the switch um has been moved to itshigh-speed position, that is, to a position at or near stop member 97,the arm 10 will thereafter act to maintain the speed of the motor EMconstant, independent of variations of the load ipon the car G. Sincethe total torque which will be exerted by the motor 12 is dependent uponthe load upon the car C, it follows that, by arranging the spring 21with a predetermined strength, the arm 10 will assume a position atwhich the torque exerted by the motor just balances the torque exertedby the spring.

The use of the series field winding GSF on the generator G, if properlydesigned, tends to impose a regulation on the speed of the motor to makethe motor speed constant under variations in load. However, at highspeeds, the eiiect of the series field winding GSF is insufficient tomaintain constantspeed regulation within accurate limits.

erating device 9 since, when the motor is operating at high speed, theswitch arm 10 will be positioned at some point intermediate thepositions, defined by the dottedlines. If the load on the car is heavy,a greater torque will be exerted by the motor 12, and the arm 10 willbe, moved to a further position, cutting out one or more of the sectionsof the resistor 58 which are illustrated as bracketed under thereference character 110. As the load diminishes, less torque is exertedby the motor 12, the spring 21 will move arm 10 to a different position,including some of those sections of the resistor designated by thecharacter 110. Thus, the full-speed position is variable in accordancewith the load on the car. Hence, with the use of myaccelerating device,the speed of the elevator motor EM will be maintained constant at highspeeds without the necessity of any additional apparatus.

If it is now desired to decelerate the car to intermediate speed, thecar switch Cs may be moved in the clockwise direction to disengagecontact members 34 and 102, thereby breaking the circuitto relay 6 andto the coil of latching member 23.

The deenergization of relay 6 breaks the circuit for the armaturewinding of the torque motor 12, the torque of which is accordinglyreduced to zero. As a result, therefore, the switch arm 10 is moved inthe counter-clockwise direction, under the influence of the spring 21,until stopped by the latching member 24, now in its extended position.Deenergization of relay 6 completes the circuit for the coil of relay 7,which cannot close, how-- ever, due to the restraint imposed by latchingmagnet 7a.

In elevators arranged to operate at comparatively highspeeds, such asfrom 500 to 800- feet per minute, it is. desirable, in the stoppingoperation, to bring the car to a slow landing speed of about, forexample, 20 to 50 feet per minute, a few feet from the floor at which itis desired to stop and to then interrupt the power supply and apply thebrake at the same point each time. If the power supply was abruptlyinterrupted, with the car operating at high speed, the rate ofdeceleration would be so rapid as to cause discomfort to the passengers.

Therefore, in the assumed example, if it is now desired. to stop thecar, the car switch G8 may be moved in the clockwise direction to apoint where contact member 34 is disengaged from contact member 98 butstill engages contact members 36, 41 and 45.

The disengagement of contact members 3 and 98 breaks the circuit to thecoil of latching member 24, which thereby permits the latching member 24to assume its normal retracted position under the influence of spring30. Switch arm 10, therefore, under the infiuence of its spring 21,moves in a counterclockwise direction to its extreme or illusstratedposition, thereby slowing the elevator motor EM from intermediate speedto slow landing speed, as determined by the value of resistor 58. Whenthe car C approaches within a predetermined distance of the floor atwhich it is to stop, the car switch C8 may be centered to disengagecontact members 36, 41 and 45 from contact member 34. Disengagement ofcontact members and 45 breaks the circuit for the up-direction switch 1which, in turn, interrupts the circuit to the separately excited fieldwinding of the generator and sets the brake (not shown) to bring the carto rest at the floor. The disengagement of contact members 35 and 41breaks the circuit for the coil of latching magnets 7 a, the core member32 of which assumes its normal position. Between the time that thelatching magnet 7a assumes its normal retracted position and the timethat contact members 35 and 36 of the car switch Ca are disengaged, thecircuit for switch 7 is completed, and no mechanical restraint isimposed upon it. However, its actuation is ineflective to supply powerto the armature windings of motor 12, since this latter cir cuit hasalready been broken at the contact members 0 and (Z of up-directionswitch 1.

After the car switch is fully centered, relay 7, of course, is againdeenergized,"and the systemis returned to normal, ready for a subsequentoperation.

In describing the efiect of the eddy-current disc 20 with respect toconditions during ac coil 20. It will be apparent, therefore, that, I ondeceleration, the first part of the counterclockwise motion of switcharm 10 will be more rapid than the last part, as. depicted by curve 109.Further, since, during deceleration, the torque of motor 12 is of zerovalue, the rate at which the switch arm 10 will move ondeceleration isgreater than the rate at which it will move on acceleration.

It will be also apparent that, by making independent adjustments of thetorque of the present assumedoperation, the action of the system wasdescribed in connection with a very slow advance and return of the carswitch Cs. It will be apparent that such slow movement is unnecessary toefiect the proper sequential relationship of the various parts, andthat, in fact, such relationship is independent of the rate at which thecarswitch handle is moved. With the type of control illustrated, it is,of course, necessary that the car switch be moved to the-proper point tocomplete the proper circuits for the various rates of speed at which itis desired to operate the car.

, Thus far, the descri tion has been confined to upward travel wit apositive load. If however, the load had been negative, or such as todrive the elevator motor as a generator to return power to the line thesituation would have been slightly ditierent. Under such conditions,since the current in the loop circuit between the armatures of thegenerator and motor would have been reversed, the direction of currentflow through coil 27 of reverse power relay 5 would have been reversed,whereas the direction of current flow through coil 28 of this relaywould have remained the same. As a result, reverse-power relay 5 wouldnot have been actuated to energize the coil of auxiliary directionswitch 3. However, under these conditions, the coil'of auxiliarydirection switch 4: would have been energized through the normallyclosed contacts of reverse-power relay 5 to complete a circuit for thearmature of torque motor 12 to send current through said armature in thereverse direction. Hence, while the direction of current flow throughthe field would have been reversed, such reversal would have beenaccompanied by a similar reversal of the armature current, and thedirection of the developed torque would have remained unchanged.

It is well known that, with a given load on the car, an elevator motorwill run at a higher rate when regenerating than when driving. Thevariation in speed from noload to full-load regenerating may be fivepircent ofvthe no-load speed of the system.

though there are other methods, one way to compensate for this speeddifi'erence isto reduce the generatorexcitation when the load isnegative. Latching member 112 is illustrative of one method. ofaccomplishing this result. As shown, under conditions of negative load,latching member 112 will extend into the path of the switch arm 10 andlimit its motion in the clockwise direction. As a result, the generatorexcitation is limited to .such value that the speed of motor EM is thesame as at no load or any value of positive load. If latching member 112is designed to be effective at from one-half to full negative load, anormal regulation of five percent will obviously be reduced to two andone-half percent. It closer regulation is desired, additional latchingmembers, as 112, may be designed to be responsive to different values ofnegative load. For purposes of simplification, one only is illustrated.

It is also apparent that a positive load in the upward direction isaccompanied by the same direction of current flow through the loopcircuit as is a negative load in the downdirection. However, it will beobserved that, while a change from positive load-to negative load in onedirection'will result in a change in direction of current flow throughonly the coil 27 of reverse power relay, a change from positive ornegative load in one direction to positive or negative load,respectively, in the other direction results in a reversal of directionof current flow in both coils 27 and 28 of relay 5. Under conditions ofreversed travel with positive load then, relay 5 will be actuated tocomplete a circuit for auxiliary switch 3. Since the direction ofcurrent flow through the field 12 is reversed, however, it

' would appear that the direction of torque of motor 12 would bereversed. It will be remembered, though, that the circuit for-thearmature winding of torque motor 12 was led through contact members 0and d of the direction switches. Thus it is that the direction switches1 and 2 operate to keep the torque of motor 12 unidirectional, asafi'ected by'changes in direction of travel of the car, while auxiliarydirection switches 3 and 4 0perate to keep the torque of motor 12unidirectional as affected by changes in the character of the load, aspositive or negative.

It is apparent then, that travel in the down direction is in allrespects similar to travel n the up direction except that down-dime tionswitch 2 replaces up-direction' switch 1.

For purposes of clarity ofdescription, I have described my invention asapplied to a manually controlled elevator. It will be apoarent however,that it is equally applicable to any known' system of automatic slowdown and stoppage of the car by means of automatic devices set intooperation by the centering of the car switch. Such a system is disclosedin a, copending application of E. M. Bouton, Serial No. 73l.921. filedAugust 14, 1924. and assigned to WVestinghouse Electric andMannfacturing Company, in which the circuits set up by movement of thecar switch are mainained through the normally-closed contact members ofinductor relays carried by the car and adapted to cooperate withinductor plates mounted in the elevator shaft adjacent to the floorlevels. to slow down and stop the car whenever the car switch iscentered to energize the exciting coils of the inductor relays.

It will also be apparent that, while I have illustrated my system asapplied to an elevator operable at a high speed, an intermediate speed,and a low landing speed, it is equallyapplicable to systems having anynumber of speeds, it being only necessary toadd additional latchingmembers, as 23 and 24, with suitable control means, to adapt my systemto as many speeds as are desired.

.The embodiment of'my invention shown and described is a preferred form,but it is to" be understood that my system is susceptible of manychanges and modifications, and I. thereto: e, do not desire to belimited to any of the details shown and described herein except insofaras defined in the appended claims.

I claim asmy invention:

1. In a motor control system, a motor, a source of power, meansforsupplying voltage from said source to said motor, voltage-modityingmeans for varying the value of voltage so supplied comprising a switcharm movable over a fixed path between two extreme positions, meansbiasing said lever to a position representing lowest voltage and meansfor eX- erting a force proportional to the load on said motor to movesaid lever against the force or said bias and means for exerting a forceinversely proportional to the degree of movement of said arm, to retardmovements of said arm.

2. In an elevator-control system, a motor. means for supplying variablevoltage to said motor, means for controlling the voltage so supplied tooperate said motor at a plurality of different speeds between zero speedand a predetermined high speed, said controlling means including aswitcharm movable to a plurality of positions, each corresponding to adifferent speed, voltage-modifying means controlled by movement of saidarm and means for progressively increasing the rate of movement of saidarm as said armmoves a different speed, voltage-modifying meanscontrolled by movements of said arm and means for progressivelyincreasing the rate of movement of said arm as said arm moves topositions of increasing speed and progressively decreasing the rate ofmovementofsaid arm as said arm moves to positions of decreasing speed.

4. In a motor-control system, a motor, a generator having. a separatelyexcited field winding for supplying variable voltage to said motor, asource of power, means for supgenerator having a separatel plyingexciting voltage to said generator including a. plurality ofvoltage-modifying means, a switch arm movable over a predetermined pathfor rendering said voltage modifyin means ineffective in smallincrements to tIiereby accelerate said motor, means for moving said armthrough distances proportional to the load on said motor, and aplurality of selectively operable means for limiting the movement ofsaid arm at a plurality of different positions.

5. In a motor-control system, a motor, a generator having a separatelyexcited field winding for supplying variable voltage to said motor, asource of power, means for supplying exciting voltage to said generatorincluding a plurality of voltage-modifying means, a switch arm movableover a predetermined path for rendering said voltagemodifying meansineilective in small increments to thereby accelerate said motor, meansfor moving said arm through distances proportional to the load on saidmotor and means for decreasingly retarding the movements of said arm assaid arm progressively renders increasing numbers of said incrementsineffective.

6. In a motor-control system, a motor, a

.generator having a separately excited field portional to the load onsaid motor, meansfor decreasingly retarding the movements of said arm assaid arm pro ressively renders increasing numbers of sai incrementsineffective, and means for variably ad ust1ng said retarding means.

7. In a motor-control system, a motor, a generator having a separatelyexcited field winding for supplying variable voltage to said motor, asource of power, means for supplying exciting voltage to said generatorincluding a plurality of voltage-modifying means, means for renderingsaid voltagemodifying means ineffective in small morements to therebyacelerate said motor to a predetermined speed within a predeterminedtime, irrespective of load conditions.

8. In a motor-control system, a motor, a excited field winding forsupplying varia le voltage to i said motor, a source of power, means forsupplying exciting voltage to said generator. including a plurality ofvoltagemodifyingmeans, means for rendering said voltage-modifying meansineffective in small increments to thereby accelerate said motor,including a switch arm movscribed my name able over a predetermined pathbetween two extreme positions, means biasing said arm to one extremeposition, a motor for moving said armagainst the force of said biasingmeans, having its armature connected for constant-voltage energizationand having its field winding connected to receive current'in valueproportional to the current supplied to said first named motor,retarding means for said arm including a magnet having opposed windingsthereon, one connected for constantvoltage energization and the otherconnected in parallel with said generator field winding.

9. In a motor-control system, a motor to be controlled, a motorcontrolling member, means actuable by an operator to control said memberfor varying the speed of operation of said motor, and means comprising aload responsive device for automatically controlling said member toregulate the rate of speed variation to be according to a predeterminedrate for all loads.

10. Ina motor-control system, a motor to be controlled, load responsivemeans, means actuable by an operator for initiating the starting of saidmotor, and means operative thereafter for rendering said load responsivemeans effective, for automatically accelerating said motor to apredetermined speed in accordance with a predetermined rate ofacceleration and for thereafter maintaining the speed constant at allloads.

11. In a motor-control system, a motor to be controlled, means actuableby an operator for initiating the starting of said motor, meansrenderedefi'ective thereafter, for automatically accelerating said motor tobring it up to any one of a lurality of speeds as predetermined by saidactuable means and for thereafter maintaining the speed constant,irrespective of the load, comprising a motor controller, and loadresponsive actuating means associated therewith.

12. In combination, an elevator car, a hoist motor associated therewith,a switch mounted on the car for actuation by the operator, meansresponsive thereto for initiating the starting of the hoist motor, andmeans comprising a load responsive device for automatically controllingthe acceleration of the motor to a predetermined speed. at apredetermined rate irrespective of the load.

13. In combination, an elevator car, a hoist motor associated therewith,a switch mounted onthe car for actuation b the operator, and meansresponsive thereto or starting or stopping said motor including loadresponsive means and a motor controller actuatedthereby forautomatically 'controllin the rate of speed variation to be in accorance with a predetermined rate irrespective of the load. I In testimonywhereof, I have hereunto subthis 22nd day of July 1929.

DANIL O SANTINI.

